1. Field of the Invention
The present invention relates to a process for extruding a calibrated profile of a thermoplastic polymer onto articles, the articles being positioned in the processing region of an automatic handling unit. The polymer melted in an extruder is fed, via a heated pressure hose, to a heated extruder head which is guided by the automatic handling unit and provided with an extrusion die, and is extruded and deposited on the articles. The invention further relates to suitable devices for carrying out this process.
2. Discussion of the Background
A process of this kind is described in EP 0 524 092 A1 for extruding a frame or a frame part onto a glass pane. From this document, it is also known, by means of this process, to apply profiles of a thermoplastic polymer, in particular of a thermoplastic elastomer, onto other articles, for example as sealing profiles on car doors, boot lids or sunroofs, and as sealing profiles or frame profiles onto articles of any other kind.
In the known process, after completion of the extrusion operation onto an article, before or during the lifting of the extruder head from the article, the volume flow of the melted polymer is interrupted by controlling the drive motor of the extruder and is only brought back into operation when, after the positioning of the next article, the extruder head has been lowered almost onto the article and has commenced its travel over the article.
This mode of operation in which the volume flow in the system is interrupted during the time span in which the articles are changed on the processing table is not free of disadvantages. Because of the inertia of the system a certain elastic deformability of the melted material and the heated hose under high pressure, and because of the melting and metering behavior of the extruder, irregularities occur in such discontinuous operation, which may lead to defective profiles and to a defective operation of the process.